Corey Stevens Truth, Lies, and O-rings: Inside the Space Shuttle Challenger Disaster Final Report

I can distinctly remember the day when the Space Shuttle Columbia broke up during

descent. It was a Saturday morning in February 2003. I was eating Lucky Charms in my living

room, flipping through the TV to find some kind of awful Saturday morning programming. Then

I happened upon MSNBC. It took a second for what I was looking at to register – the Space

Shuttle Columbia has broken up during descent over Texas. All crew were lost. My dad was at

the grocery store, and I called him. I called my grandparents. I knew at that moment that human

spaceflight would never be quite the same.

Most of us think back to the Challenger disaster in 1986 and see how things went wrong.

A faulty o-ring caused a massive explosion. Though Challenger exploded two years before I was

born, I was well-acquainted with the disaster. I had always been somewhat of a spaceflight buff,

and Challenger was one of the most significant disasters in the history of human spaceflight. I

had read up on the disaster through Wikipedia, I had watched specials on TV. My stepmother

had told me stories about the disaster: she was a Miami student at the time, and when she walked

into class, the professor (in tears) let the class go, saying, “We lost Challenger.”

The loss of the space shuttle (then considered to be one of the most reliable vehicles in

existence) was a shock to everyone. Well, mostly everyone. Allen J. McDonald was the man in

charge of the production of the shuttle’s solid rocket boosters (SRBs) at Morton Thiokol, Inc., a

Utah-based company dealing in rubber, chemicals, and rocket technology. Subsequent to the

disaster, he became the scapegoat for the disaster both by NASA and his own company.

McDonald’s book, Truth, Lies, and O-rings: Inside the Space Shuttle Columbia Disaster tells an

unbiased story of the events leading up to and subsequent to the disaster. With the help of author

James R. Hansen, McDonald’s book tells a tragic tale of apathy and ignorance by both NASA

officials and management at Morton Thiokol.

McDonald opens his book by describing the process by which he became the Director of

Shuttle Operations at Morton Thiokol. From the very beginning he begins to paint a picture of

negligence at his company, describing situations where tests were flubbed and results were

altered. One particular event he describes was the testing of a new type of SRB material. The

booster was parallel to the ground and underwent a full

usage test. Upon the completion of the test and the

inspection afterward, it was found to be in perfect working

order, with no problems concerning o-rings or any material

degradation. When McDonald went to his boss to share the

good news, his boss informed him that he had tampered with

the booster by using more putty than usual to seal the joint.

Though McDonald eventually convinced his boss to redo the

test, this picture of management at Morton Thiokol

continues throughout the book.

To clarify, let me describe how the solid rocket

boosters work. Other than the shuttle itself, the two SRBs

are reusable parts of the launch system. They contain solid

rocket fuel, which upon ignition boots the shuttle and

external fuel tank into orbit. They are made up of multiple

sections, joined together in a clevis-tang system (think

hardwood floors) at the Vehicle Assembly Building (VAB),

side-by-side with the shuttle. Partway into the flight, the

SRBs jettison (detach) from the shuttle and external tank,

Corey Stevens Truth, Lies, and O-rings: Inside the Space Shuttle Challenger Disaster Final Report

which continues on under the power of the shuttle’s liquid fuel motors. The SRBs then use

parachutes to fall back to Earth, where they are recovered by ships. The joints are then taken

back to Cape Canaveral where they are partially broken down and sent by train to Morton

Thiokol’s production center in Utah. Morton Thiokol then inspects the SRBs for any anomalies.

In short, the system works like this: each section of an SRB is assembled on-site at the

VAB. Each joint has two o-rings, which a rubber-ish seal that prevent hot gasses from escaping

the joint and damaging anything outside the SRB. The o-

ring closest to the inside of the SRB is the primary o-ring,

and the o-ring closest to the outside of the SRB is the

secondary o-ring. This system was developed by Morton

Thiokol to be redundant in case of the failure of the

primary o-ring. At the time, the use to two o-rings was

unprecedented in rocket technology. The joints, once put

in place and sealed with o-rings, are then sealed with a

zinc-based epoxy.

Challenger was lost when both o-rings on the right

SRB failed. Just after ignition, gray smoke was seen coming out of the lower joint, evidence the

seal was not happening. Due to the extremely cold weather the metal of the SRB warped,

relegating both o-rings to being useless. An oxide deal (the result of burned fuel) plugged the

gap, allowing the SRB to continue functioning. Around 53 seconds into the flight, the shuttle

encountered extremely strong wind sheers. These sheers shattered the oxide deal and a jet of hot

gas shot out, melting a component that held the SRB in place. The SRB then pitched forward and

impacted the external fuel tank. The external fuel tank, now compromised, began to quickly burn

its liquid fuel. Being the main structural component of the launch system, the external fuel tank,

once compromised, allowed for the disintegration of the shuttle. The subsequent explosion was

catastrophic. 73 seconds into the flight, Challenger was gone.

This all was preventable, McDonald claims. Problems with the o-rings in the SRBs were

known as far back as 1984, two years before the launch and loss of Challenger. McDonald

describes in vivid detail the problems Morton Thiokol has encountered. In short, four of the six

shuttle flights in 1984 showed anomalies in the o-rings. The main problem was blow-by,

meaning instances in-flight where hot gasses momentarily bypassed the primary o-ring, relying

on the secondary o-ring to stop them. This was evidenced by soot between the two o-rings. In

addition to blow-bys, some of the o-rings were also experiencing erosion, sometimes up to 20%

of the ring diameter. Though this concerned officials at Morton Thiokol, including McDonald,

their confidence in the redundant system allowed space shuttles to continue to fly.

The launch date for Challenger’s final flight was January 28,

1986. Being the senior Morton Thiokol official at Cape Canaveral,

McDonald was required to participate in flight readiness reviews

(meetings during which various officials give a go/no-go for launch).

The morning of January 28 was to be the coldest launch of a space

shuttle at that point – the ambient temperature was around freezing

(32°F). McDonald knew that the lowest threshold for o-ring operation

was 40°F, and that below that there was “insufficient data to show the

o-ring would seal properly.” On the previous coldest shuttle flight

(STS-51C, Discovery) the temperature had been 53°F. On this flight,

Morton Thiokol found, there was significant blow-by and charring seen

Corey Stevens Truth, Lies, and O-rings: Inside the Space Shuttle Challenger Disaster Final Report

on the secondary o-ring.

The night before Challenger’s launch, McDonald told NASA he would not give a go for

launch. NASA, eager to launch the space shuttle, went over McDonald’s head, receiving

authorization from McDonald’s boss. They requested the authorization in writing, unprecedented

at the time. This desire to have written authorization, claims McDonald, shows NASA’s

hesitance to launch the shuttle in such cold conditions.

After the disaster, McDonald knew he was in a tight spot. He began to systematically

catalogue his daily life, including all contact made with other people. When President Regan

formed the Rodgers Commission to investigate the disaster, McDonald became one of the most

important figures in the investigation. Morton Thiokol, knowing his knowledge would be critical

of the company, demoted him and tried to keep him quiet. It was only after the Rodgers

Commission realized this that he was able to regain his old position. McDonald went on to

become the man in charge of redesigning the SRB to be more reliable.

Redesigning the SRBs was done under intense government and media scrutiny.

McDonald describes the stresses of dealing with so many people, saying he often was unable to

sleep. Despite his obviously compromised mental state, Morton Thiokol was able to successfully

redesign the SRBs. This included the use of another clevis joint between the propellant and the

outside, as well as adding a third o-ring to make the system triply redundant.

Overall, this was an absolutely fascinating book about a tragic topic. It is obvious

McDonald is a good writer, and I often felt the pain or joy he was going through. To have such a

thorough account of our nation’s first in-flight space fatalities is truly wonderful, despite the

implications. McDonald’s writing style is easy to follow, but his work often gets bogged down in

alphabet soup (which, ironically, he despises). It was sometimes difficult to follow the

progression and remember the names of all the people involved. It seemed sometimes that he

would get off-topic discussing something that was of relatively small importance. One would

hope that NASA and its management would learn from something as catastrophic as this.

Despite having gone through three years of restructuring, it would be the falling foam observed

on the next flights after Challenger that would lead to America’s next space catastrophe.